Such a steering is, for example, known from U.S. Pat. No. 6,102,150.
The invention concerns a so-called “steer-by-wire” steering, in which a steering member does not act directly upon the steering motor arrangement, but firstly generates a signal, which again activates a steering valve controlling the supply of hydraulic fluid to the steering motor arrangement.
For safety reasons, it is often necessary to provide several steering circuits or at least several steering valves in such steer-by-wire steering systems. If one of the steering valves does not work properly, the other steering valve is activated, so that the vehicle can still be steered.
In the case known from U.S. Pat. No. 6,102,150, each steering circuit is provided with an additional valve, which interrupts or releases the steering circuit. This additional valve can be located in the flow direction upstream or downstream of the respective steering valve. When a changing over from one steering valve to the other is desired, both additional valves should possibly be changed over simultaneously, meaning on the one hand that the vehicle remains steerable, on the other hand, however, that the fault in one steering valve cannot get through to the other steering valve. Realising this, however, requires relatively large efforts.